Conical roller transmission



2 Sheets-Sheet 1 z. y; wElsEL. coNIcAL ROLLER TRANSMISSION JNVENTOR.

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Oct. 6, 1959 Filed May 28, 1956 Oct. 6, 1959 z. v. wElsEL.

coNIcAL ROLLER TRANSMISSION 2 Sheets-Sheet 2 Filed May 28, 1956 Arx/4L )www x f of icuii am: 4x15, d -d R./. MM. m IK 5 A A W.. L y B nited States Patent ice CONICAL ROLLER TRANSMISSION Zenas V. Weisel, Los Angeles, Calif. Application May 28, 1956, Serial No. 587,826

9 Claims. (Cl. 74-200) The present invention relates generally to transmissions and more particularly to a novel and improved conical roller transmission. v t

In` my co-pending patent application Serial No. 363,606, tiled June 23, 1953, now PatentNo. 2,748,614, issued June 5, 1956, there is disclosed a conical roller transmission incorporating a pair of coaxial driving and driven discs which are bridged by a plurality of conically profiled rollers. The rollers are each supported by mounting means that include a universal mounting for the roller and a tiltable member connecting the uni- Versal mounting to the transmissions frame. The transmission is so designed that during rotation of the discs the rollers normally tend to assume a position wherein the axis of rotation of each roller intersects the axis of rotation of the discs. When it is desired to vary the relative speed .of the discs, the angularity of the rollers relative to the discs is changed. This change in angularity is accomplished by tilting each of the rollers until its aXis of rotation no longer intersects the axis of rtation of the discs. The rollers will then automatically move bodily to their new ratio position wherein their axes of rotation again intersect the axis of rotation of the discs. This arrangement permits the surface of the rollers in contact with the surfaces of the discs to undergo substantially skid-free rolling movement in a spiral path along the latter surfaces as the rollers move from one ratio position to another. As pointed out in my copending patent application unless the rollers can undergo such skid-free rolling movement, they must be forcibly skidded between ratio positions. Such skidding of the rollers over the discs gives rises to three major disadvantages. (a) It necessitates a comparatively low power capacity so as to avoid complete loss of traction during a change in ratio as the rollers are skidded from one position to another, (b) it requires a very heavy control force to urge the rollers to skid between ratio positions, and (c) the rate at which the ratio positions undergo change must be comparatively slow so as to avoid damage to the traction surfaces of the rollers and the disc members.

It is a major object of the present invention to pro- Y vide a conical roller transmission generally similar to that covered by my above-identified application but incorporating a different roller mounting structure. The structure of the present invention permits the rollers to undergo substantially skid-free rolling movement between ratio positions and generally affords the same advantages as that disclosed in my above-mentioned prior application.

Another object of the present invention is to provide a conical roller transmission which is extremely efficient at all speeds and under all load conditions.

An additional object of the invention is to provide a conical roller transmission which is capable of transmitting a maximum amount of power for a minimum weight and size.

lt'is another object to provide a conical roller trans- '2,907,220 Patented Oct. 6, 19,59

mission wherein tracking of the rollers on the discs is relatively insensitive to dellections, differential expansion,

4tolerance variations in machining and to variations in power load.

Yet an additional object of the invention is to provide a conical roller transmission which is compact and Another object is to provide a conical roller transmission which is simple in design and rugged of construction whereby it may afford a long and trouble-free service life.

These and other objects and advantages of the present invention will become apparent from the following detailed description, when taken in conjunction with the appended drawings, wherein:

Figure l is a longitudinal vertical sectional view of a A preferred form of conical roller transmission embodying element 44 of the latter assembly the present invention;

Figure 2 is a vertical sectional view taken on line 2-2 of Figure 1; f Figure 3 is a front view showing the movement followed by a roller as its ratio position is changed; and

Figure 4 is a side view showing such roller movement. Referring to the drawings, the preferred form of conical roller transmission embodying the present invention broadly comprises a frame or casing C which independently rotatably supports a driving or input disc I and a driven or output disc O. These discs are formed with spaced-apart opposed concave surfaces of revolution approximating a toric section and designated 10 and 12, respectively. The driving disc I is connected to a drive` shaft 14 by a torque responsive thrust varying means V, while the driven disc 'O carries a splined sleeve 16 for receiving an output shaft (not shown). A plurality of conically profiled rollers R are interposed between the disc members I and O. Each of these rollers R is formed with a convex surface 18, bridging the concave surfaces 10 and 12 of the input and output discs I- and O. The rollers R are each supported by a rollercarrying member M. A trunnion Tis interposed -between each roller-carrying member M and the frame C. Rotation of the driving disc I is transferred to the driven disc O by means of the rollers R, the driven disc O rotating in the opposite direction from the driving disc,I. Variation of the relative speeds of hte two discs is accomplshed by effecting a change in the angularity of the. rollers R relative to the discs, as indicated yby the dotted showing of the rollers in Figure l. v

More particularly, the casing C is of annular transverse cross-section having an outer wall 24, a removable front wall 26 and an integral rear wall 28. The front wall 26 is formed with a coaxial opening 30 whereinis disposed a retainer cup 32. A seal ring 34 is interposed between the front Wall and the front portion of this retainer cup. The retainer cup ,32' encompasses theouter element 40 of a ballbearing assembly 42. The inner p y encompasses a boss 45 formed on the drive shaft 14. A exible, dished-disc type pre-load spring46 is interposed between the rear portion of the retainer cup 32 and a shoulder 37 formed in the front wall 26. This pre-load spring 46 constantlyv exerts a rearwardly acting` force upon the retainer :cup 32 for a purpose to be described hereinafter.

The torque responsive thrust varying means V may be similar -to -one of the forms disclosed in my abovedescribed co-pending application Serial No. 363,606. It should be particularly observed, however, that other types of ftorquelresponsive thrust varying -means Amay be ernployed 4without departing from the scope'of the present invention. 'The lparticular type of torque responsive thrust varying means disclosed herein is of theangular contact cam type and includes a -retainer V50 for a-plurality-of balls 52. As shown Iin Figure l, the-inner racewa-y 'S4-for these balls.52 is formed of the rear end of the drive shaft -14. The outer raceway 56 is formed at thei'frontportion'of the driving disc I. This outer raceway56 includes apluralityof pockets deiinirig cam surfaces-which are inclined axially relative to `the axis `of rotation of the two discs. The mode of operationof the torque responsive thrust varying means V .will be fully setV forth hereinafter.

The -rearwall 28is formed with an inwardly directed annular flange 60 that encompasses the outer element-'62 of the rear ball-bearing assembly 64. The inner element 66 of the rear ball bearing assembly encompasses the output sleeve 16. The rear wall 28 Ais coaxially formed with an annular opening 67 for receivingthe output sleeve -16.

Each of the trunnion members 'I includes a screw element 68 having `a cylindrical body 70 from each end of which extends a stub shaft, the latter being designated 72fand 74. As shown in Figure 2, the stub shafts 72 and.'74 'are iournaled within a pair of ears 76 and 78 constituting integral inward extensions of the outer wall 24 of the casing C. Roller bear-ings 80 are AVinterposed between the stub shafts and aligned bores -82lformed through the ears 76 and 78. With particular reference toFigure 2, the right-hand stub shaft 74 is longer than the left-hand stub shaft '72 and is keyed to a hypoid gear 84 by means of a pin 86. The screw element 68 may be centered relative to the casing C and the discs I and O by a pair of set screws 88 and 90 which are carried-by opposed plugs 92 and 93, respectively, that are removably affixed to the casing C by snap rings 94. The-body-70 of thescrew element 68 is formed with a spiral groove 96 dening a screw thread. k

The roller-carrying members M each include a nut element 98 formed with a coaxial bore 100 thatY receives the cylindrical body of a screw element 68 of a trunnion member YT. Each bore 100 is formed with a spiral groove 102which is complementary to the spiral groove 96 formed in the body of the screw element 68. A pluralitysof balls 103 are disposed within thev grooves 96 and 102. The outermost grooves of the nut element 98 are interconnected by a ball return tube 104. "The radiallysinner portion of the nut element 98 slidably supports aradia'lly extending shaft 105 for movement in a Yplane parallel to the axis of rotation of the discs I and O. Thus, the-radially outer end of the shaft-105 is formed with-a square-boss 106 that is'slidably disposed within a slideway 107 formed in the yradiallyiniuer vportion of the nut-element 98. With this arrangement, the rollers Rzare permitted to undergo a slight amount oi axial movement relative to the casing C so as to follow the axial shifting of the driven disc O under varying load conditions. `Theshaft 105 receives the inner elements 110 ofa'pair of axial thrust type ball bearing assemblies 112 andi114. The outer-elements 115 of these bearing 'assemblies` are fitted -within a coaxial cavity '116 formed in one ofthe rollersv R. With this arrangement, the radially'outwardly :directed forces to whichthe-rollers R are subjected are transferred to the'casing C'- through the nut='elements98, screw elements 68 andgthe ears 76 and-78.

Referring again to Figure l, eachhypoid gearl84`vv is formed with teeth117- that areengaged with complementary--teeth-11S-'formed` inrthe outer periphery of a controlhring 120. The "control ring 120 is coaxially rotatably supported within the casing C by a support ring 122 having `its outer portion rigidly aixed to the casing. The adjoining surfaces of the control and support rings are formed with complementary semi-circular grooves 124 and 126 wherein are disposed a plurality of ball elements 128. The control ring is adapted to undergo limited rotation in either direction under the influence of a manually orautomatically operated control system (not shown).

In the operation of the aforedescribed transmission, the preload spring 46 constantly biases the front ball bearing assembly 42 and the drive shaft 14 rearwardly towards the -drivendisc Oso as to obtain preloading of rollers against the-discs and of the torque responsive thrust varying means V. Upon the application of torque upon the drive shaft 14 above that which through cam action will equal the thrust load of the preload spring 46 resisted by an approximately equal torque of the output disc-,0, the ballsSZ will tend-to cam the driving disc I-rearWardly-, Ior-tothe left in=Figure '1, so as to increase the pressure of the driving disclagainst the rollers Rand of thelatterragainstthe driven discO. The greater-the torquethe larger the force effected by thetorque responsive 'means V tendingto'create-a thrust urging the driv- -ing disc I-rearwardly. Withvthis arrangemenLthe contact-pressureoffthe rollers R -against thekconcave surfaces 10v and 12 ofthe discs I-and O will be automatically regulated.

When it lis desired toV change the relative speeds of the ldriving and-drivendiscs I and O the control ring 120 -will be-rotated-througha limited number of degrees in the directionnecessary-toeiect such. change. yReferring now to Figure 3,-such-rotation Vof the control ring 120 will effect concurrent-rotation of each ofy the hypoid gears 84 andhence of the screw elements. Rotation ofthe screw elements-68 serves to effect concurrent movement of each of the nut elements 98 along the'longitudinal axis of each screw element. VIn this manner, each of the rollers R willbe caused to move along a straight path normal to a plane containing the axis of rotation of the discs and parallel to theaxis of rotation of the rollers. This roller movement is shown in Figure 3, the roller 'R being normally disposed in its dotted outline position of this gure and being caused to undergo axial movement to its solid outline position therein upon rotation of lthe screwl element 68.

lAs indicated in Figure 3, the axis of rotation r-r of eachv roller 5R normally intersects the axis of rotation d-d of the discs I and VO. Rotation of the control ring 120, however, will cause this roller to be moved to the left inthe mannerdescribed immediately hereinabove until its axis of rotation r-r is displaced to oneside of the axis of rotation d--d of the discs as indicated by reference numerals r'-r. lIt will be observed that the `axis of rotation of the rollers, however, remains in a plane parallel tothe axis vof rotation of thediscs both during and after-such movement of the roller, which plane is gradually displaced from the axis of rotation of the discs to a point -to one side thereof. durnig such roller movement. When the roller .has been moved to its solid outline position of` Figure 3 in .preparation for a change to a new ratio position, it will be in a state of unbalance relative tothe discs, inasmuch as each of the rollers normally tend to assume a position in which its axis of rotation intersects that of the discs so long as the discs are undergoing rotation.

In order for the system to again reach a state of balanice, the roller R, and hence the nut element 98, will swing bodily about the longitudinalpaxis of the screw element 68 from the dotted outline position ,of Figure 4 to the solidV outline position` therein. Such swingingmction causes the nut element v98 toscrew itself to theright relative to'FigureBuuntil the axis ,of rotation rf-rof .the roller R again intersects the axis of rotation tif-dof fiile discs I andV O. V. The rolleri Rwill thusautomaticallynbe moved to its new ratio position. Moreover, during such m'ovement the convex surface 18 of the roller R in contact the concave surfaces and 12 of the rotating discs will undergo substantially skid-free rolling movement in a spiral path along the latter surfaces. When the rollers R reach their new ratio position, the system Will again be in a state of balance and little if any force must be applied through the control system in order to maintain the rollers in such new position.

While there has been shown and described hereinbefore what is considered to be the preferred embodiment of the present invention, various changes and modications may be made with respect thereto without departing from the spirit of the invention or the scope of the following claims.

I claim:

l. A conical roller transmission, comprising: a frame;

Va pair of independently rotatable coaxial driving and driven discs formed with spaced-apart opposed concave surfaces of revolution approximating a toric section; a conically proled roller interposed between said discs and formed with a convex surface bridging the concave surfaces thereof; a trunnion member carried by said frame and having a screw element extending along a longitudinal axis substantially normal to the axis of rotation of said discs and spaced radially outwardly therefrom; a roller-carrying member rotatably supporting said roller with the axis of rotation of said roller being normal to the longitudinal axis of said trunnion member and the axis of rotation of said roller normally intersecting the v axis of rotation of said disc members, said roller-carrying member having a nut element engaged with said screw element whereby said roller-carrying member is movable relative to said trunnion member along the longitudinal axis thereof upon rotation of said screw element; and control means for rotating said screw element so as to effect movement of said roller-carrying member relative to said trunnion member along the longitudinal axis thereof until the axis of rotation of said roller no longer intersects the axis of rotation of said discs in preparation for a change to a new ratio position wherein said axes will again intersect, said roller automatically moving bodily to said new ratio position with its surface in contact with the surfaces of said discs undergoing substantially skid-free rolling movement in a spiral path along the latter surfaces as said discs are rotated.

2. A conical roller transmission, comprising: a frame; a pair of relatively axially shiftable, independently rotatable, coaxial driving and driven discs formed with spacedapart opposed concave surfaces of revolution approximating a toric section; a conically profiled roller interposed between said discs and formed with a convex surface bridging the concave surfaces thereof; a trunnion member carried by said frame and having a screw element extending along a longitudinal axis substantially normal to the axis of rotation of said discs and spaced radially outwardly therefrom; a roller-carrying member having a Shaft rotatably supporting said roller with the axis of rotation of said roller being normal to the longitudinal axis of said trunnion member and the axis of rotation of said roller normally intersecting the axis of rotation of said disc members, said roller-carrying member having a nut element engaged with said screw element whereby said roller-carrying member is movable relative to said trunnion member along the longitudinal axis thereof upon rotation of said screw element, and said shaft being movable relative to said frame parallel to the axis of rotation of said discs in order that said roller may follow relative axial shifting of said discs; and control means for rotating said screw element so as to effect movement of sai-d roller-carrying member relative to said trunnion member along the longitudinal axis thereof until the axis of rotation of said roller no longer intersects the axis of rotation of said discs in preparation for a change to a new ratio position wherein said axes will again intersect, said roller automatically moving bodily to said new ratio position with its surface in contact with the surfaces of said discs undergoing substantially skid-free rolling movement in a spiral path along the latter surfaces as said discs are rotated.

3. A conical roller transmission, comprising: a frame; a pair of independently rotatable coaxial driving and driven discs formed withspaced-apart opposed concave surfaces of revolution approximating a toric section; a conically profiled roller interposed between said discs and formed with a convex surface bridging the concave surfaces thereof; a roller-carrying membervrotatably supporting said roller with the axis of rotation thereof located in a plane parallel to the axis of rotation of said discs and the `axis of rotation of said roller normally intersecting the axis of rotation of said discs; screw and nut means interposed between said frame and said rollercarrying member for effecting bodily movement of said roller-carrying member along an axis substantially normal to the axis of rotation of said discs and spaced outwardly therefrom until the axis of rotation of said roller no longer intersects the axis of rotation of said discs in preparation for change to a new ratio position wherein said axes will again intersect, -said roller-carrying member automatically swinging relative to said frame in a plane parallel to the axis of rotation of said discs and said roller automatically moving bodily to said new ratio position with its surface in contact with the surfaces of said discs undergoing substantially skid-free rolling movement in a spiral path along the latter surfaces as said discs are rotated; a control ring supported by said frame for limited rotation in either direction; and gearing interposed between said screw and nut means and said control ring whereby rotation of said control ring will eifect concurrent rotation of said screw means as said discs are rotated.

4. A conical roller transmission, comprising: a frame; a pair of independently rotatable coaxial driving and driven discs formed with spaced-apart opposed concave surfaces of revolution approximating a toric section; a conically profiled roller interposed between said discs and formed with a convex surface bridging the concave surfacesl thereof; a trunnion member carried by said frame and having a screw element extending alo-ng a longitudinal axis substantially normal to the axis of rotation of said discs and spaced outwardly therefrom; a roller-carrying member rotatably supporting said roller with the axis of rotation of said roller being normal to the longitudinal axis of said trunnion member and the axis of rotation of said roller normally intersecting the axis of rotation of said disc members, said roller-carrying member having a nut element engaged with said screw element whereby said roller-carrying member is movable relative to said trunnion member along the longitudinal axis thereof upon rotation of said screw element; a control ring rotatably supported by said frame; and gearing interposed between said screw element and said ring whereby rotation of said control ring will effect concurrent rotation of said screw means so as to effect movement of said roller-carrying member relative to said trunnion member along the longitudinal axis thereof until the axis of rotation of said roller no longer intersects the axis of rotation of said discs. in preparation for a change to a new ratio position wherein said axes will again intersect, said roller automatically moving bodily to said new ratio position with its surface in contact with the surfaces of said discs undergoing substantially skidfree rolling movement in a spiral path along the latter surfaces as said discs are rotated.

5. A conical roller transmission, comprising: a frame; a pair of relatively axially shiftable, independently rotatv able, coaxial driving and driven discs formed with spacedvapart opposed concave surfaces of revolution approximating a toric section; a conically profiled roller interposed between said discs and formed with a convex suri7 lface .bridging the concave surfaces thereof; a trunnion Amember carried by .said frame and having' a .screw .element Vextending along a Vlongitudinal axis substantially 4normalitotheaxis of rotation of said discs and .spaced outwardly therefrom; a roller-carrying member having a shaft rotatably supporting said roller with the axis of yrotation of said roller being normal Lto the longitudinal .axis of said trunnion member land the axis of rotation of said roller normally intersectingthe axis of rotation of said disc members, said roller-carrying member'having a nut element engaged with said screw element whereby .said roller-carrying member is movable relative to said utrunnionmernber along the longitudinal axis thereof upon rotation of said screw element, and said shaft being vmovable relative to said frame parallel Vto the axis of rotation of said discs in order that said roller may .follow relative axial shifting of said discs; a control .ring -rotatably supported by said frame; `and gearing interposed ,between said screw element and said ring wherebyrotation of said control ring will effect concurrent rotation `of said screw means so as to effect movement of said roller-carrying member relative to said trunnion member along the longitudinal axis thereof until the axis ofrrotaytion of said roller no longer intersects the axis of Arotation of said discs in preparation for a changeto anew ratio position wherein said axis will again intersectsa id roller automatically moving bodily to `said new ratio. position with its surface in contact with the surfaces of said discs undergoing substantially skid-free rollingmovement a spiral path along the latter surfaces as said discs are rotated. i

6. A conical rollertransmission, comprising: a frame; a .pair of independently rotatable coaxial driving and driven discs formed with spaced-apart opposed concave surfaces of revolution approximating a toric section; a conically profiled roller interposed between said'discs .and formed with a convex surfaclevbridging the concave'surfaces thereof; a trunnion member carried-by saidfframe and having a screw element, the longitudinal axis ofsaid screw element beingsubstantially normal to the axisof rotation of said discs and spaced radially outwardlytherefrom; a roller-carrying member having a nut elementencompassingsaid screw element, saidnut v.element `being formed witha radially extending shaft knormal tothe -longitudinal axis of said `screw element which supports saidroller, the axis of rotation of said roller normally intersecting the axis of rotation of said disc members; complementary grooves formed in the confronting surfaces Aof said screw and nut elements and deningla screw thread;.ball elements disposed within said grooves; andcontrol means connected to said trunnionrmember forrotating said screw element so as to effect movement of said nut element relative thereto along the-longitudinal axis thereof until the axis of rotation of saidrollerfno longer intersects the axis of rotation of said discs in preparation for a change to a new ratio position wherein said axes will again intersect, said roller automatically moving bodily to said new ratio position with its surfacein contact with the surfaces of saidvdisc undergoing vsubstantially skid-free rolling movement in a spiral path along the latter surfaces as said discs are rotated.

7. A conicalroller transmission, comprising: a-frame; a pair of independently rotatable coaxial drivingand driven discs formed with spaced-apart opposed concave surfaces of revolution approximating a torio section; a Conically profiled roller interposed between said .discs andformed with a convex surface bridging the concave surfaces thereof; a trunnion member .having a 'screw element which includes a cylindrical body from .both ends of which extendsa stub shaft, the longitudinal axis of said cylindrical body being substantiallynormal to theaxis of rotation of said discs ,and spaced .outwardly therefrom; means formed on said framejournalling said stub shaft; a roller-carrying member .having a nutelernent encompassing saidscrew element,lsaid nutrelement being `of extends .a .stub ,said lcylindrical z#sarai-roll ,intersecting the axis of rotation of said disc members; a ll.gear keyed to .one grooves :formed on theconfronting surfaces of said screW landinut elements and defining a screw thread; a ball- ,axis ofvrotation of said roller no r of rotation of said discs in preparation fora change to la newvratioposition wherein said axes will again intersect,

`formed .with a radially extending shaft normal to the ylongitudinal axis of said cylindrical body for supporting said -roller, the axis of rotationof said roller normally intersecting 2the axis of rotation of said disc members; a

to said trunnion member along the longitudinal axis of said cylindrical body until the axis of rotation lof said roller Vno Vvlonger intersects vthe axis of `rotation of said discs in preparationfor a change to a new ratio position wherein said axes will again intersect, said roller automat'ically moving bodily vto said new ratio position with its surface in contact with the surfaces of said `Vdiscs undergoing substantially skid-free rolling movement in a spiral path .along the latter surfaces V.as said Vdiscs are rotated.

.8. "A conical .roller transmission, comprising: a frame;

.a pairlofindependently rotatablecoax-ial driving and drivdiscs formed ,with spaced-apart opposed concave surfaces of revolution approximating a toric section; a

conicallyproled roller interposed betweensaidY discs landiormed .with .a convex surface bridging the concave `:surfaces thereof; a

trunnion member having a screw Y, lementgwhichincludes acylindrical body frombothwends n shaft, the longitudinal yaxis of body being substantially normalV to the .axls .of rotationof said discs .and spaced outwardlyV theremeans .formed on said framejournalling said stub shafts; a .roller-carrying member having a nut element Aencornpassing said screw element, said nut element being .formed with a radially extending shaft normal to die 4:lor'igitudinal axisof said cylindrical `body for supporting er, .the axis ofrotation of said roller normally of .said stub shafts; complementary return tube interconnecting the outermost grooves in .said nut element; ball elements disposed within said grooves; .and a control ring rotatably journaled by said lframe andengaging said gear whereby rotation of said control ring will effect concurrent movement of said roller carrying member relative to said trunnion member along the longitudinalaxis of said cylindrical body until the longerl intersects the axis said kroller automatically moving bodily to said new ratio position with its surface in contact with the surfaces of said discs undergoing substantially skid-free rolling lmovfementin a spiral path along therlatter surfaces as .said 4discs are. rotated.

9. A conical roller transmission, comprising: a frame; a

.pair of relatively axially shiftable, independently rotatable,

coaxial n driving and driven discs formed with lspacedapart opposedconcave surfaces of revolution approximating a -ftoric section; a conically profiled .rollerl interposed between said-discs and formed with a convex surface-.bridging the concave surfaces thereof; aftrunnion member'having a screw element which includes a cylindrical body from both ends of which extends a stub shaft, the longitudinal axis of said cylindrical body being substantially normal to the axis ofrotation 'of said discs vand spaced outwardly therefrom; means formed on said frame journalling-said stub shafts; a roller-carrying memberhaving anut.v element encompassing said screw element, the radially inner portion of said nut element being formed .with a slideway;` a radially extendinggshaftgsup- `portingsaid roller-with the axis of rotation of said roller normalglyintersecting the axis of rotation of said disc members,.. the .radially outer portion of said shaft being 4formed'with .a bossthat is slidably disposed within said slideway .in Qorderthat s aid roller may Yfollow relative axial shifting of said discs; a gear keyed to one of said stub shafts; complementary grooves formed on the confronting surfaces of said screw and nut elements and dening a screw thread; a ball-return tube interconnecting the outermost grooves in said nut element; ball elements disposed within said grooves; and a control ring rotatably journaled by said frame and engaging said gear whereby rotation of said control ring will effect concurrent movement of said roller-carrying member relative to said trunnion member along the longitudinal axis of said cylindrical body until the axis of rotation of said roller no longer intersects the axis of rotation of said discs in preparation for a change to a new ratio position wherein said axes will again intersect, said roller auto# matically moving bodily to said new ratio position with its surface in contact with the surfaces of said discs undergoing substantially skid-free rolling movement in a spiral path along the latter surfaces as said discs are rotated.

References Cited in the le of this patent UNITED STATES PATENTS France Sept. 12, 1951 

